05-12-09-Write Buffer

This page discusses the write buffer patch related to an infinite loop trying to remove elements from the write buffer.<br>

== The Problem ==

The loop that controlled emptying the write buffer (when detected as full) compared the first element against sim_cycle to see if it were less than sim_cycle and can be removed. However, if the write buffer became empty through this, it would continue to try to delete these elements.

== The offending code ==
From commit:
 if((MD_OP_FLAGS(contexts[context_id].LSQ[contexts[context_id].LSQ_head].op) & (F_MEM|F_STORE)) == (F_MEM|F_STORE))
 {
  if(cores[core_num].write_buf.size() == cores[core_num].write_buf_size)
  {
   <b>while(*(cores[core_num].write_buf.begin()) < sim_cycle))</b>
   {
    cores[core_num].write_buf.erase(cores[core_num].write_buf.begin());
   }
  }

== Corrected Code ==
The while needs to check that the buffer is not empty first.
 if((MD_OP_FLAGS(contexts[context_id].LSQ[contexts[context_id].LSQ_head].op) & (F_MEM|F_STORE)) == (F_MEM|F_STORE))
 {
  if(cores[core_num].write_buf.size() == cores[core_num].write_buf_size)
  {
   while(<b>!cores[core_num].write_buf.empty() && </b>(*(cores[core_num].write_buf.begin()) < sim_cycle))
   {
    cores[core_num].write_buf.erase(cores[core_num].write_buf.begin());
   }
  }